JP3300534B2 - Electronic circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic circuit including a current mirror circuit, and more particularly to a feed-forward technique for supplementing an operation speed of the current mirror circuit.

[0002]

2. Description of the Related Art Conventionally, in an analog integrated circuit, a current mirror circuit is usually used as a means for turning back a signal current. By connecting the base electrode or gate electrode and the emitter electrode or source electrode of multiple transistors in common, if the dimensions of those transistors are equal, a current equal to the external current applied to the input transistor is output. It is a circuit that can flow as if it were reflected on the transistor on the side.

[0003] However, when the current mirror circuit is configured using a PMOSFET or a pnp transistor, the PMOS
The operating frequency of the electronic circuit including the current mirror circuit has been limited due to the limitation of the element operating speed of the T and pnp transistors.

On the other hand, "A CMOS WIDEBAND AMPLIFIER WITH
800MHz GAIN-BANDWIDTH, "Proceedings, IEEE 1991 Cus
As shown in FIG. 2 (b) of the tom Integrated Circuits Conference, a method has been devised in which a feed-forward path using a capacitor is provided in the configuration of the folded cascode circuit instead of the current mirror circuit.

In this conventional example, a low-frequency signal current passes through a grounded gate circuit composed of a resistor and a PMOSFET, and a high-frequency signal passes through a grounded gate circuit composed of an NMOSFET through a feed-forward path of capacitance. As a result, PMOSFETs with poor high-frequency characteristics can be avoided, so that the overall high-frequency characteristics can be improved.

However, in such a method, a circuit for generating a bias voltage of the gate or base of the transistor for grounded gate or grounded base constituting the folded cascode circuit is separately required, which not only complicates the design but also increases the circuit scale. There was a disadvantage that it became larger.

[0007]

As described above, in the conventional method using the folded cascode circuit, it is necessary to separately provide a gate ground circuit and its bias circuit in order to improve the operation speed in a high frequency region. An object of the present invention is to provide an electronic circuit having a high frequency characteristic including a current mirror having a small circuit scale.

[0008]

In order to achieve the above object, the present invention provides an electronic circuit including a current mirror circuit, wherein at least a gate electrode or a base electrode of a transistor through which an input current of the current mirror circuit flows. A low frequency signal passing means is connected, and an element constituting an output stage of the electronic circuit and an input terminal of the current mirror circuit are connected via a high frequency signal passing means.

Preferably, the apparatus further comprises a low-pass filter for limiting a band of a control signal applied to at least a gate or a base of a transistor through which an input current of the current mirror circuit flows, and an input terminal of the current mirror circuit and the current terminal. -A feed-forward path is constituted by a capacitance between the terminal and another terminal in the electronic circuit including the mirror.

[0010]

With the above arrangement, in an electronic circuit including a current mirror circuit, a control signal whose high frequency component is limited by a low-pass filter is applied to a gate of a transistor through which an input current of the current mirror circuit flows. Therefore, the input impedance of this current mirror circuit is low at low frequencies, but operates as a constant current source at high frequencies, so that its input impedance is high.

At this time, a feed-forward path is provided by a capacitor between the input of the current mirror circuit and the other terminal of the electronic circuit, so that a signal is transmitted through the current mirror at a low frequency. The signal is transmitted, but at a high frequency, the signal is transmitted via a feed-forward path by the capacitance. Therefore, a signal is transmitted at a high frequency without passing through a current mirror circuit, so that characteristics at a high frequency can be improved.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of an electronic circuit including a current mirror circuit to which the present invention is applied. The current mirror circuit CM1 in the electronic circuit 1 includes transistors MPC1 and MPC2 and a low-pass filter L1. The drain of the transistor MPC1 through which the input current flows in the current mirror circuit CM1 is
Connected to the gate of the transistor MPC2,
Transistor MPC1 via low-pass filter L1
Connected to the gate.

The low-frequency component input to the current mirror circuit hardly flows through the feed-forward path because the impedance of the capacitor CF forming the feed-forward path is high at low frequencies. Since the drain voltage of the transistor MPC1 is transmitted to the gate of the transistor MPC1 through a low-pass filter at a low frequency, the operation of a normal current mirror circuit is performed, and the input current is turned back by the transistor MPC2.

On the other hand, the drain voltage of the transistor MPC1 is cut off by the low-pass filter L1 at a high frequency and is not transmitted to the gate of the transistor MPC1.
Operates as a current source, and the input impedance of the current mirror circuit increases. Therefore, the high-frequency component input to the current mirror circuit flows through the feed-forward path since the impedance of the capacitor CF forming the feed-forward path is low at high frequencies.
Since it is transmitted bypassing the current mirror circuit,
The high frequency characteristics of the electronic circuit 1 can be improved. Further, as compared with the case where the conventional folded cascode is used, the circuit scale can be reduced because the gate ground circuit and the bias circuit associated therewith are not required.

FIG. 2 shows a second embodiment in which the present invention is applied to an amplifier circuit. In FIG. 2, transistors MN1,
MN2 forms a differential pair, and each gate has positive and negative inputs I
n +, In-. The differential input signal is applied from positive and negative inputs In + and In-. The current source I1 supplies a current to the differential pair. At low frequencies, the output currents of the differential pair will be in the respective current mirror circuits CM2, CM3
And the current turned back by the current mirror circuit CM2 is turned back by the normal current mirror circuit constituted by the transistors MN3 and MN4, and output to the output terminal Output together with the current turned back by the current mirror circuit CM3. Is done.

In the current mirror circuits CM2 and CM3, the control voltage applied to the gates of the transistors MP2 and MP4 is band-limited by a low-pass filter.
The input impedance of M3 increases, and the high-frequency component of the output current of the differential pair is fed forward to the output or a node close to the output via the capacitors CF1 and CF2 forming the feed forward path. In this way, signals can be transmitted at high frequencies by bypassing the current mirror circuit composed of PMOSFETs.
Thus, it is possible to prevent the performance such as gain from deteriorating in the current mirror circuit constituted by. In addition, since a grounded gate circuit is not required, a grounded gate circuit and a bias circuit associated therewith are unnecessary, and the circuit scale can be reduced.

Further, as shown in FIG.
3. In the current mirror circuit composed of MN4, the control voltage is applied to the gate of the transistor MN3 via the low-pass filter L4, and the capacitance C
Peaking can also be performed at a high frequency by setting the impedance at the node at the feedforward destination by F2 to increase as the frequency increases, similarly to the current mirror circuits CM2 and CM3.

The low-pass filters L2 to L in FIG.
4 are resistors R2 to R4 and capacitors C2 to C4 as shown in FIG.
Can be easily realized. Further, as shown in FIG. 5, the gate capacitances of the transistors MP2, MP4 and MN3 and the resistances R2 to
R4 may constitute low-pass filters L2 to L4. At this time, as shown in FIG. 6, for example, the polysilicon constituting the gate of the transistor MP2 in the current mirror circuit CM2 may be extended to R2.

FIG. 7 is a circuit diagram of the current mirror circuit shown in FIG. 5 in order to increase the output impedance of the current mirror circuit.
Transistors MP1 to MP4, M constituting a mirror circuit
The resistors RS1 to RS6 are connected in series with the sources of N3 and MN4, respectively.
Are connected. At this time, as shown in FIG. 7, the feed forward destination by the capacitor CF1 may be the source of the transistor MN4.

FIG. 8 shows that the resistors RS1 to RS6 in FIG. 7 are connected to transistors MPR1 to MPR4, MNR1 and MNR2.
In the example realized in the above, the resistances RS1 to RS
6 can be reduced in area. In FIG. 8, the gates of the transistors MPR2, MPR4, and MNR1 are shared with the gates of the transistors MP2, MP4, and MN3, respectively. However, as shown in FIG.
2, MP4 and MN3 from the resistors R2b to R2, respectively.
4b.

FIG. 10 shows a modification of FIG. 5 in which a cascode configuration is used to increase the output impedance of the current mirror circuit. The transistors MP2, MP4, MP6, and MP2 through which the input current of the current mirror circuit flows.
8, the gates of MN3 and MN5 have resistors R2 to R7 which form a low-pass filter with the gate capacitance of the transistor.
Are connected in series. In FIG. 10, similar to FIG. 6, the same effect can be obtained by using the source of the transistor MN4 as the feedforward destination by the capacitor CF1.

FIG. 11 is a modified example using a current mirror circuit having a different cascode configuration in FIG. 5 and shows a transistor MP2 through which an input current of the current mirror circuit flows.
To the gates of MP4 and MN3, resistors R2 to R4 that constitute a low-pass filter with the gate capacitance of the transistor are connected in series. In FIG. 11, the same effect is obtained by using the source of the transistor MN4 as the feedforward destination by the capacitor CF1 as in FIG.

FIG. 12 shows "A High-Swin" in FIG. 5 in order to increase the output impedance of the current mirror circuit.
g, High-Impedence MOS Cascade Circuit, "IEEE Journ
This is an example of using a regulated cascode circuit described in al of Solid-State Circuit, vol. 25, Feb. 1990. The transistors MP11 and MP13 and the current source I2 increase the output impedance of the current mirror circuit CM2, and the transistors MP12 and MP14 and the current source I3 increase the output impedance of the current mirror circuit CM3. Also, transistors MN7, MN8
Thus, the output impedance of the current mirror circuit including the transistors MN3 and MN4 and the resistor R4 in the current source I4 is increased. In FIG. 12, the same effect is obtained by using the source of the transistor MN7 as the feedforward destination by the capacitor CF1.

FIG. 13 shows a modification in which the feed-forward destination by the capacitor CF2 in FIG. 12 is set to the gate of the transistor MN7, and the high-frequency component fed forward through CF2 is also feed-forwarded through CF1. High-frequency components are also included in the transistor MN7.
Output to the output terminal Output only through
The transit time of the high-frequency component to the output terminal Output becomes almost equal, and the phase characteristics in the high-frequency region are further improved as compared with the example of FIG.

The present invention can also be applied to a differential output amplifier circuit. For example, in FIG. 14, the transistors MN1, MN
2 form a differential pair, and each gate has positive and negative inputs In.
+, In-. The differential input signal is applied from positive and negative inputs In + and In-. The current source I1 supplies a current to the differential pair. At a low frequency, the output current of the differential pair is turned back by each of the current mirror circuits CM2 and CM3, and the output terminal Out is output using the current sources I6 and I7 as loads.
Output to put + and Output-.

FIG. 15 is a circuit diagram of FIG.
And the gate capacitance of the transistor MP2, L3 is connected to the resistor R3
This is an embodiment configured with the gate capacitance of the transistor MP4.

FIG. 16 shows an embodiment in which the regulated cascode circuit shown in FIG. 15 is used. The feedforward destination of CF1 and CF2 is the source of transistors MN12 and MN11, respectively. Also,
As shown in FIG. 17, the feed forward destination may be the gates of the transistors MN11 and MN12.

The embodiment in which only the signal applied to the gate of the transistor through which the input current of the current mirror circuit flows is limited by the low-pass filter has been described. As shown in the seventeenth embodiment of FIG. , The transistor MPC through which the output current of the current mirror circuit CM1 flows
2 is also applied to the low-pass filter L1.
2 to limit the influence of the gate capacitance of the transistor MPC2 through which the output current of the current mirror circuit flows at the input terminal of the current mirror circuit.

FIG. 19 shows an eighteenth embodiment in which the present invention is applied to an amplifier circuit. Referring to FIG.
N1 and MN2 form a differential pair, and each gate is connected to positive and negative inputs In + and In-. The differential input signal is applied from positive and negative inputs In + and In-. Current source I1
Supplies current to the differential pair. At low frequencies, the output currents of the differential pair are each current mirror circuit CM2,
Turned back at CM3, and furthermore the current mirror circuit CM2
Is turned back by the current mirror circuit including the transistors MN3 and MN4 and the low-pass filter L4, and is output to the output terminal Output together with the current turned back by the current mirror circuit CM3.

In the current mirror circuits CM2 and CM3, the control voltages applied to the gates of the transistors MP2 and MP4 are low-pass filters L22 and L32, respectively.
At high frequencies,
The input impedance of the mirror circuits CM2 and CM3 increases. Furthermore, the low-pass filters L21 and L31 can reduce the reduction in impedance at high frequencies due to the gate capacitance of the transistors MP1 and MP3 at the inputs of the current mirror circuits CM2 and CM3.
Therefore, the high-frequency component of the output current of the differential pair is feed-forwarded to the output or a node close to the output via the capacitors CF1 and CF2 that efficiently form the feed-forward path. Since the signal can be transmitted at a high frequency by bypassing the current mirror circuit formed by the PMOSFET, it is possible to prevent the performance such as gain from deteriorating in the current mirror circuit formed by the PMOSFET. Also, since no gate grounding circuit is required,
There is no need for a gate ground circuit and the accompanying bias circuit,
Circuit size can be reduced.

Referring to FIG. 19, transistor MN
3 is supplied with a control voltage via a low-pass filter L4 to control the feed voltage of the capacitor CF2.
Peaking is applied at a high frequency by setting the impedance at the forward destination node to increase as the frequency increases, similarly to the current mirror circuits CM2 and CM3.

FIG. 20 shows a nineteenth embodiment in which the low-pass filter in FIG. 19 is realized by the gate capacitance and resistance of a transistor.
This is an example. In the seventeenth embodiment shown in FIG. 18, a low-pass filter for limiting the band of a signal applied to the gate of the transistor constituting the current mirror circuit is separately provided, but as shown in the twentieth embodiment in FIG. The same effect can be obtained by using two low-pass filters.
FIG. 22 is an example applied to an amplifier circuit, and FIG.
Is an example in which the low-pass filter in FIG.

While the embodiments of the electronic circuit constituted by using MOS transistors have been described above, the present invention can be similarly applied to bipolar transistors. For example, the circuit of FIG. 4 can be similarly realized by replacing the pnp transistor and the npn transistor as shown in FIG.

[0034]

As described above, the input impedance of the current mirror circuit is set to increase as the frequency increases, so that the high frequency component of the input current can be reduced by the output or the output via the capacitor forming the feed forward path. Feed forwarded to node near output. Since the signal can be transmitted at a high frequency by bypassing the current mirror circuit formed by the PMOSFET, it is possible to prevent the performance such as gain from deteriorating in the current mirror circuit formed by the PMOSFET.
In addition, since a grounded gate circuit is not required, a grounded gate circuit and a bias circuit associated therewith are unnecessary, and the circuit scale can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a second embodiment when the present invention is applied to an amplifier circuit.

FIG. 3 is a third embodiment which is a modification of the second embodiment shown in FIG. 2;

FIG. 4 is a fourth embodiment in which the low-pass filter in the third embodiment shown in FIG. 3 is specifically constituted by a resistor and a capacitor.

FIG. 5 is a fifth embodiment in which the capacitance constituting the low-pass filter is realized by the gate capacitance of the transistor in the fourth embodiment.
Example.

FIG. 6 is a modified example of the fifth embodiment in which the resistance constituting the low-pass filter is realized by the polysilicon constituting the gate of the transistor in the fourth embodiment.

FIG. 7 shows a sixth embodiment in which a resistor is connected in series to the source of a transistor constituting a current mirror in the fifth embodiment, and the feed-forward path is changed.

FIG. 8 shows a seventh embodiment in which the resistor connected in series to the source in the sixth embodiment is realized by the ON resistance of a MOS transistor.

FIG. 9 is an eighth embodiment showing a modification of the seventh embodiment;

FIG. 10 shows a ninth embodiment in which the present invention is applied to an amplifier circuit including a cascode-type current mirror circuit.

FIG. 11 shows a tenth embodiment in which the present invention is applied to an amplifier circuit including a cascode-type current mirror circuit.

FIG. 12 shows an eleventh embodiment in which the present invention is applied to an amplifier circuit.

FIG. 13 is a twelfth embodiment in which the feed-forward path is modified in the eleventh embodiment.

FIG. 14 shows a first example in which the present invention is applied to a differential output amplifier circuit.
Three examples.

FIG. 15 is a diagram showing a fourteenth embodiment in which the low-pass filter in the thirteenth embodiment is specifically constituted by a resistor and a gate capacitance of a transistor.

FIG. 16 shows a first example in which the present invention is applied to a differential output amplifier circuit.
5 Examples.

FIG. 17 shows a seventeenth embodiment in which the feed forward path is modified in the sixteenth embodiment.

FIG. 18 shows a seventeenth embodiment of the present invention.

FIG. 19 shows an eighteenth embodiment in which the present invention is applied to an amplifier circuit.

FIG. 20 is a nineteenth embodiment according to the eighteenth embodiment, in which the low-pass filter is specifically constituted by a resistor and a gate capacitance of a transistor.

FIG. 21 is a twentieth embodiment of the present invention.

FIG. 22 is a twenty-first embodiment in which the present invention is applied to an amplifier circuit.

FIG. 23 is a diagram illustrating a twenty-second embodiment in which a low-pass filter is specifically configured by a resistor and a gate capacitance of a transistor in the twenty-first embodiment.

FIG. 24 is a diagram showing an example in which the circuit shown in FIG. 4 is realized using bipolar transistors.

[Explanation of symbols]

1: Electronic circuit including current mirror circuit CM1 to CM3: Current mirror circuit in which the control voltage applied to the gate of the transistor through which the input current flows is band-limited by a low-pass filter L1 to 4, L11, L12, L21 , L22, L31,
L32: low-pass filter CF, CF1, CF2: capacitance forming a feed-forward path C2-4: capacitance forming a low-pass filter R2-4, R2a-4a, R2b-4b, R21, R2
2, R31, R32: resistance forming a low-pass filter RS1 to 6: resistance M to: MOSFET T to: bipolar transistor I1 to 7: current source VDD, VCC: positive power supply VSS, VEE: negative power supply In: current mirror Circuit input Out: output of current mirror circuit In +: positive input of amplifier circuit In−: negative input of amplifier circuit Output: output of amplifier circuit Output +: positive phase output of amplifier circuit Output−: reverse phase output of amplifier circuit

Continuation of the front page (56) References JP-A-57-185711 (JP, A) JP-A-51-26447 (JP, A) JP-A-1-93207 (JP, A) JP-A-4-130807 (JP) JP-A-5-67928 (JP, A) JP-A-61-282512 (JP, A) JP-A-3-65715 (JP, A) JP-A-4-248707 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) H03F 1/42 H03F 3/343 H03F 3/345

Claims (7)

(57) [Claims] In an electronic circuit including a current mirror circuit, low frequency signal passing means is arranged between a control electrode of a transistor forming an input portion of the current mirror circuit and a control electrode of a transistor forming an output portion of the current mirror circuit. By arranging high-frequency signal passing means between the input terminal of the input unit of the current mirror circuit and the output stage of the electronic circuit,
An electronic circuit characterized in that a main transmission path of a low-frequency signal component and a main transmission path of a high-frequency signal component are separated. 2. An electronic circuit including a current mirror circuit, wherein a low-frequency signal passing means is connected to at least a gate electrode or a base electrode of a transistor through which an input current of the current mirror circuit flows, and an output stage of the electronic circuit is provided. And an input terminal of the current mirror circuit is connected through high-frequency signal passing means. 3. An electronic circuit including a current mirror circuit, further comprising: a band limiting circuit for a control signal applied to at least a gate or a base of a transistor through which an input current of the current mirror circuit flows. An electronic circuit, wherein a signal transmission path is formed by a capacitive element between an input terminal and another terminal in the electronic circuit. 4. The electronic circuit according to claim 3, wherein said band limiting circuit includes a low-pass filter circuit composed of a resistor and a capacitor. 5. The electronic device according to claim 3, wherein said signal transmission path comprises a capacitance element having a capacitance larger than a capacitance value of a capacitance element constituting a low-pass filter circuit included in said band limiting circuit. circuit. 6. The low-pass filter circuit according to claim 4, wherein a band is limited by a capacitance value of a gate capacitance or a base capacitance of at least a transistor through which an input current of the current mirror circuit flows. Electronic circuit as described. 7. The low-pass filter circuit includes a resistance element having a resistance larger than a parasitic resistance of a base electrode or a gate electrode of a transistor through which an output current of the current mirror circuit flows. The electronic circuit according to claim 4 or 5, wherein